Contact brushes are commonly used in connection with collectors or slip rings which are rotary electrical contacts used in for example many different types of electric motors or electrical generators.
The contact brush is placed in a so called brush holder in which a spring is typically used to maintain a contact pressure towards the slip ring. The spring steadily pushes the brush downwards towards the slip ring as the brush wears down. The holder thus provides for a stable support of the contact brush in a proper position in relation to the collector or slip ring and provides means for applying contact force on the brush.
An assembly of several brush holders may be mounted in parallel across the surface of a collector or slip ring. These brush holders usually have individual clamps and tension adjustments for each brush.
One such basic brush holder is disclosed in U.S. Pat. No. 2,804,558, wherein two brushes may be mounted in parallel and where so called hammers are arranged to provide for applying pressure to hold the brushes in contact with the collector or slip ring. Each of the hammers is provided with means for providing a tensioning action on the hammer exerting a constant pressure on the brush. These means may comprise a flat spring or any other type of elastic member.
Different diameters of slip rings make contact with the collector in different ways, and at different angles and the holder may thus be designed to provide the proper contact angle for the brush.
It is important that the pressure on the different brushes is constant such that the brushes wear evenly.
Today, slip ring arrangements are commonly used in wind power plant units, which are often placed at remote locations for instance at sea. There is therefore an increased need for a brush holder that can accommodate several brushes mounted in parallel, and which does not require as much maintenance in terms of keeping an even pressure on the brushes in order to provide an optimal contact between the brush and slip ring.